JPH0299408A - Radial tire - Google Patents

Abstract

PURPOSE:To increase heat radiation effect to increase durability at high-speed and anti-wear property by forming siping of a specified form and size extending in radial direction of a tire at a butt-less portion joined with the side edge of a tread. CONSTITUTION:Siping S is formed in the circumferential direction of a tire at the upper part of a side wall 4 joined with the side edge a of a tread 5, i.e., at a butt-less portion 9. The siping S is so formed that it extends starting from a small distance L of more than 4mm and below 6.5mm, its length W in radial direction is more than 1.5% and below 7.5% of the tire section height H, its max, width t in the circumferential direction is below 3mm, and that its depth N from the surface of the butt-less portion 9 in a direction perpendicular to that surface is more than 5mm and below 10mm. Also, the S is so positioned that its said max, width t is positioned at the middle of the said length W and its shape is made in a spindle smaller in diameter in outward and inward radial directions.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention can extend the life of tires by suppressing the occurrence of uneven wear in the tread portion and increasing the heat dissipation performance of the shield side portion, and is particularly applicable to trucks, buses, etc. The present invention relates to a radial tire that can be suitably used as a heavy vehicle tire.

[Conventional technology]

With the development of the expressway network, opportunities for vehicles, especially heavy vehicles such as trucks and buses, to use expressways will increase.
In addition to high-speed performance, extended wear life is desired.

However, high-speed durability is limited by the temperature rise caused by internal heat generation in the tread, especially in the shield side. Therefore, in order to improve high-speed durability, the rubber thickness in the trend section must be reduced. However, such a reduction in rubber thickness reduces the allowable wear thickness of the tire, reducing wear life.

In this way, high-speed durability and wear life are contradictory characteristics.

On the other hand, because the shield side part of the tire generates more heat than the crown side part, and the amount of slippage with the road surface is relatively large, the amount of wear of the shield part is greater than that of the crown side part. So-called shoulder-drop wear occurs, which is larger than the above. Tire life is also limited by this drop-off wear, so it is desirable to improve the shoulder-drop wear resistance in a well-balanced manner in addition to high-speed durability and wear resistance.

In order to solve one part of this problem, the present applicant disclosed in Japanese Unexamined Patent Application Publication No. 61-235206 that a pneumatic radial tire for heavy vehicles has a pattern around the periphery by arranging cut grooves in parallel on the shoulder side portion. We proposed a tire based on a directional stiffness index of 30 to 70 and a cut groove volume index of 2.5 to 15.

Note that the circumferential stiffness index of a pattern is the ratio of the circumferential stiffness of the tread portion without cut grooves to the circumferential stiffness of the block between the cut grooves when cut grooves are provided, and The groove volume index is the ratio of the total volume of the cut groove to the volume of the shielder side portion from the tread surface to the groove bottom, and by setting these within the above range, the circumferential rigidity is reduced and heat generation is suppressed. At the same time, by minimizing the decline in wear resistance due to the reduction of circumferential rigidity, it is possible to increase high-speed durability and wear resistance, and at the same time improve ground conformity in the shield side part. This is intended to reduce shoulder drop wear.

[The problem that the invention attempts to solve! However, as proposed above, when a tire with a large number of cut grooves arranged in parallel on the cylinder side is mounted on the front wheel of a rear-wheel drive vehicle, that is, on the travel side, as shown in Fig. 5. As shown in the example, block B between grooves A
It has been found that so-called step wear, in which the edge portion C on the traveling direction T side is worn, may occur relatively early in use. This means that the tires attached to the idler wheels are
Based on the axle load, a resistance in the opposite direction to the traveling direction acts on the ground contact surface, and therefore, regardless of whether the vehicle is accelerating, decelerating, or running steadily, block B is A deformation occurs in which the tire falls down into the cut groove A on the opposite side of the tire traveling direction T. Moreover, this falling deformation is caused by the edge portion C
As a result of locally increasing the ground pressure at the edge portion C
It is presumed that the above-mentioned step difference is caused by so-called heel-and-toe wear. Furthermore, this uneven wear has a negative effect on tire life.

Therefore, the present invention improves high-speed durability and abrasion resistance, and reduces shoulder drop wear by appropriately relaxing the tire circumferential rigidity and increasing the heat dissipation effect without using such cut grooves. It can reduce step wear, especially on trucks,
The present invention aims to provide a radial tire which is suitable for use as a tire for heavy vehicles such as buses, and which can also be used for other radial tires and which improves the various performances mentioned above.

[Means to solve the problem]

The radial tire of the present invention includes a belt disposed radially outward of a carcass folded by a bead core and inward of a tread, and a belt disposed radially inward from the side edge on a buttress portion of the tire continuous to a side edge of the tread. 4 or more cranes and 6
．． Sivings S extending radially inward from positions separated by a short distance of 5fi or less are spaced apart in the circumferential direction, and the sivings have a radial length W of 1.5 of the tire cross-sectional height H. % or more and 7.5% or less, the maximum medium t in the circumferential direction is 3+w or less, and the depth N in the normal direction from the surface of the buttress portion is 5f1 or more and 10 days or less.

[Effect]

In this way, the siving provided in the buttress portion and extending in the tire radial direction can repeatedly increase and decrease the internal volume by compressive deformation of the tread when the tire contacts the ground and restoring deformation of the tread when the tire releases the ground.

Therefore, due to the breathing effect caused by the increase and decrease, the internal air is forced to circulate with the outside air, and the internal heat generated in the shoulder side portion due to tire rotation is effectively dissipated and cooled, thereby increasing the high-speed durability of the tire.

In addition, this sizing moderately reduces the circumferential rigidity of the shield side portion and equalizes the ground contact pressure, thereby reducing uneven wear such as shoulder drop wear and suppressing heat generation itself. Moreover, as described above, such siving can suppress the temperature rise in the shield side portion, and as a result, it is possible to increase the rubber thickness of the tread, and the wear life can be extended.

In addition, from the viewpoint of maintaining tire strength and increasing the effect of suppressing temperature rise, the siving is located at a position radially inward from the tread side edge at a distance of 4 or more and 6°5fi or less. 7. It is formed as a starting point, and its radial length W is 1.5% or more of the tire cross-sectional height H.
5% or less, the maximum width in the circumferential direction is 3mm or less, and
It is necessary to form the layer with a depth N of 5n or more and 10w or less. Further, it is more preferable that the sivings have a spindle shape that tapers inward and outward in the radial direction and are spaced apart by circumferential cuts P of 10 mm or more and 15 mm or less.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment of the present invention, which is a tire of size 10.00R20, and the tire 1 has a bead 3 through which a bead core 2 passes, and a sidewall 4 that is connected to the bead 3 and extends outward in the radial direction of the tire. , and a tread 5 joining the outer edge of the sidewall 4. The tread 5 also has a vertical groove 6.6 and a tire equator C that divide the trend 5 into a crown side portion 5A and a shield side portion 5B.
It has a rib-type trend pattern consisting of vertical grooves 7 passing through O, and the vertical grooves 6.7 can be of various shapes continuous in the circumferential direction, such as straight, zigzag, wavy, etc. I can do it. Further, in the upper part of the sidewall 4 that is connected to the side edge a of the tread 5, that is, in the buttress part 9, sivings s- that extend inward in the tire radial direction are provided at intervals in the inner circumferential direction of the tire.

Furthermore, the tire 1 includes a carcass 10 using a plurality of carcass plies made of metal cords that fold the bead core 2 from the inside to the outside of the tire, and a first reinforcing layer 11 that covers the folded part 10A of the carcass 10. , second reinforcing layer 1
2 are arranged.

The first reinforcing layer 11 is made of a metal cord, and extends from the bottom of the bead 3 to the outside of the tire, thereby reinforcing the bead 3. Note that the terminal 11 of the first reinforcement 7111
a can also be set higher than the terminal 10a of the carcass 10. Further, the second reinforcing layer 12 is provided at the end 1 of the carcass 10.
By wrapping the terminal 11a of the first reinforcing layer 11 together with 0a, the carcass 10 is prevented from blowing through, and
It is preferable to use an organic fiber cord as the second reinforcing layer 12 to prevent stress concentration at each terminal 10a, lla.

Further, the bead core 2 has a folded part 10 of the carcass 10.
A bead apex 13 with a triangular cross section extending in the radial direction is provided between the bead 3 and the main body 10B.
Increase the rigidity of.

Further, the tread 5 is provided with a belt 14 located on the radially outer side of the carcass 1o.

The bell) 14 has a width in the range of 80 to 95% of the tread width, which is the length between the side edges a and a of the trend 5, and reinforces the tread 5 over substantially the entire width. Bell) 14 is
At least one using a low stretch cord such as a metal cord
In this example, it is formed using four briars, with two briai cords oriented to intersect with each other at an angle range of 10 to 25 degrees with respect to the tire equator CO, and the other two briai cords By alternately overlapping them in a direction that intersects with each other in an angle range of 40 to 70 degrees to form a triangular structure, the rigidity of the tread portion can be increased, and the improvement in rigidity can contribute to improving the abrasion resistance of the tread rubber.

In this example, as shown in FIG. 2, among the four braais, the second braai 14a from the inside in the radial direction is medium-wide compared to the other braais, and the fourth braai 14b is made medium-wide from the other braais. By forming the belts in between, the terminal positions of adjacent braais are different, and stress concentration at the ends of the belt 14 is alleviated. Also, the radially outer outer surface of the belt 14 and the end of each briar are coated with a protective layer 15, thereby reducing the occurrence of brie peeling.

Further, the buttress portion 9 has sivings S...- extending radially inward from a position radially inwardly separated by a path ML from the side edge a and having an appropriate pitch P in the circumferential direction. It will be installed separately.

Such sizing S moderately reduces the rigidity of the shoulder side portion 5B and equalizes the ground contact pressure of the shoulder side portion 5B, thereby suppressing the occurrence of uneven wear such as shoulder drop wear. This reduction in rigidity can reduce heat generation associated with tread deformation during ground contact. This reduction in heat generation has been confirmed by an experiment disclosed in Japanese Patent Laid-Open No. 61-235206.

In addition, Sibing S uses the breathing effect of the internal volume increase/decrease due to compressive deformation Q and restoring deformation R of the tread 5 during tire contact/release to force the internal air to circulate with outside air, effectively cooling the tire temperature. can.

Here, in the sizing S, the short distance I4 is 4 mm.
Formed with a starting point of 6.5 m or more and 6.5 m or less,
Also, its radial length W is 1.5% of the tire cross-sectional height H.
It is necessary that the maximum weight t in the circumferential direction is 3 fl or less, and the depth N in the normal direction from the surface of the buttress portion 9 is 5 mm or more and 10+n or less.

When the length W is less than 1.5% of the tire cross-sectional height H and when the depth N is less than 50, the breathing rate of the siving S is insufficient, resulting in poor heat dissipation and insufficient tire stiffness mitigation effect. This causes uneven wear.

Further, if the short distance (1) exceeds 6.5, the heat dissipation cannot be effectively achieved, and the effect of alleviating tire rigidity is insufficient, promoting uneven wear.

In addition, when the short distance I is less than 4.5, when the length W exceeds 7.5% of the cross-sectional height H of the tire, when the maximum weight t in the circumferential direction exceeds 3wX, and when the above-mentioned depth If N exceeds Now, the tire rigidity will be excessively reduced, the tire strength will be reduced, and the life of the tire will be shortened.

In addition, the sizing S has the heaviest part located at the middle part of the length W, and is formed into a spindle shape that tapers outward and outward in the radial direction, so that the sizing side wall when the tread 5 is compressed and deformed. The curved deformation of S1 and S1 can be reliably performed toward both sides, and the above-mentioned breathing action can be ensured.

Furthermore, in this example, the sizing S has a maximum depth N at a position near the maximum weight t, and the groove bottom is formed in a smooth arc shape so that the depth gradually decreases toward the inside and outside in the radial direction. This prevents stress concentration at the groove bottom due to repeated deformation of compression/restoration of the tread 5.

The formation pitch P of the sizing S is preferably equal intervals or irregular intervals, such as a barrier pull pitch, in the range of 10 m or more and 15 n or less. When the pitch P is 10 dragon grooves, the tire It reduces the strength and also 1
When it exceeds 5 mm, the heat storage effect between the sivings S1S increases and the tire internal temperature increases.

Incidentally, such siving S is not only a tire having a lip type tread pattern as in this example, but also a tire having a tread 5 with one end opening at the buttress portion 9 and extending in the axial direction of the tire, as shown in FIG. A lug groove 8 whose end ends within the shoulder side portion 5B can be formed, or it can be provided in a tire having a plug-type or lug-type tread pattern, and in such a case, the sizing S. - When the sizing SA overlaps or is close to the lug groove 8, another sizing SA of a small length can be provided in place of the sizing S at the pitch position where the sizing SA overlaps or is close to the lag groove 8. Also this Cyving SA
is not limited to the above-mentioned size range, and its size can be set as appropriate based on the balance between the groove width and groove depth of the lug groove 8.

(Specific example) A tire with a tire size of 10.00R2014PH without the structure shown in Figures 1 and 2 and based on the specifications in Table 1 was manufactured as a prototype, and the tire temperature and durability of the prototype tire were measured using an indoor durability drum. The tire temperature was compared.
JIS 100% standard wear is significantly reduced. Furthermore, this stiffness relaxation also helps to suppress heat generation itself, and in addition to the heat dissipation and cooling effects mentioned above, it also suppresses the temperature rise in the shoulder side part, making it possible to increase the trending rubber thickness. It can have many effects such as extending wear life.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing one embodiment of the present invention, Fig. 2 is a perspective view showing an enlarged buttress portion, Fig. 3 is a route diagram showing the action of siving, and Fig. 4 is another embodiment of the present invention. FIG. 5 is a perspective view illustrating an example, and FIG. 5 is a side view illustrating step wear. 2- bead core, 5...trend, 9...
・Buttress part, 1 (L-・Carcass, 14・−Belt, a・−・Side edge, H・−・Tire cross section height, L−・Small distance, N・
-・Depth P・-・Pinch, S-・・Siving,
Toe/maximum medium, W/- length. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Naemura End of the second layer belt bridle 14a when a tire loaded with a positive load is transferred at a speed of 80 km/h and the internal temperature reaches a saturated state The temperature at the top is measured, and the measured temperature is expressed as an index with the conventional product as 100. The smaller the index, the lower the temperature. In addition, the durability is 100% internal pressure filled and J15140
% load was applied to the tire at an initial speed of 80 km/h, and the speed was amplified with a step width of 101 n every 2 hours.
The time for the final step leading to destruction is expressed as an index with the conventional product set as 100. The larger the index, the better the durability. [Effects of the Invention] The radial tire of the present invention, like the ridges, can effectively dissipate and cool the rubber heat generated on the shoulder side due to tire transfer due to the breathing effect of the siving provided in the buttress part, and improve the high-speed durability of the tire. can increase In addition, the sizing moderately reduces the rigidity in the circumferential direction on the shoulder side,
By equalizing the ground pressure of tires, uneven wear such as shoulder drop wear can be prevented.

Claims (1)

[Scope of Claims] 1. A belt disposed radially outward of a carcass folded by a bead core and inward of a tread, and a belt disposed radially inward from the side edge on a buttress portion of the tire continuous to a side edge of the tread. Sivings S extending radially inward from a position separated by a small distance L of 4 mm or more and 6.5 mm or less are spaced apart in the circumferential direction, and the sivings have a radial length W equal to the cross section of the tire. 1.5% of height H
or more and 7.5% or less, the maximum width in the circumferential direction is 3 mm or less, and the depth N in the normal direction from the surface of the buttress portion is 5 mm or more and 10 mm or less. 2 The sizing S has a spindle shape that tapers inward and outward in the radial direction by locating the maximum width at the middle part of the length W, and the sizing is 10 mm.
The radial tire according to claim 1, characterized in that the radial tire is spaced at equal or unequal intervals in the circumferential direction with a pitch P in the circumferential direction in a range of not less than 15 mm.